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• Tangevold, Ingeborg Braskerud; Szilagyi, Petra Agota; Amedjkouh, Mohamed & Pupo, Rafael Cortez Sgroi (2024). Synthesis of bioinspired bidentate N-ligands and their incorporation into UiO-67. Universitetet i Oslo. Full text in Research Archive Show summary

  Atmospheric methane is one of the main drivers of global warming today. Transforming methane to methanol has been suggested as a strategy to lower the anthropogenic release of methane, since methanol is more easily handled as a fuel and more versatile as chemical feedstock. Thus, a catalyst that can oxidise methane to methanol directly and selectively has been sought after for years. Particulate methane monooxygenases (pMMOs) and lytic polysaccharide monooxygenases (LPMOs) are two groups of enzymes that can activate C-H bonds to selectively form alcohols; both utilise N-ligated copper as cofactor, and can be used as blueprints for designing novel catalysts for selective methane oxidation. This work sought to synthesise ligands inspired by the active sites of pMMOs and LPMOs and immobilising them in the tunable and robust UiO-67 metal-organic framework (MOF). Specifically, three bidentate N-ligands were synthesised in this work, all were designed in a manner that let them double as functionalised linkers for the UiO-67 framework, and two of the ligands were also added hydrophobic functionality. The ligands were formed through synthetic routes of four to six steps with total yields of 28-51 %. Methods such as the Suzuki coupling, reductive amination and ester hydrolysis were employed. Through their ability to act as functionalised linkers for UiO-67, all three ligands were also incorporated into crystalline, porous and thermally stable mixed-linker UiO-67 type MOFs, in which 16.7-19.7 % of the linkers were functionalised. Incorporation of the functionalised linkers led to some decrease in the thermal stability and porosity of the MOFs, but not detrimentally. MOF integration of the ligands was done through post-synthetic linker exchange (PSLE), since the ligands decomposed during attempts at direct synthesis of the mixed-linker UiO-67 MOFs. Due to the increased bulkiness of ligands containing hydrophobic functionality, PSLE with these had to be performed at elevated temperatures to obtain the desired degree of linker exchange.

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